Method for controlling a fastener driving tool

A method of controlling a fastener driving tool, the fastener driving tool comprising:

• a power source;
• a control module electrically connected to the power source;
• a cylinder assembly comprising a first cylinder, a second cylinder pneumatically connected to the first cylinder, a first piston which is reciprocally movable and disposed in the first cylinder, and a second piston which is reciprocally movable and disposed in the second cylinder, the first piston defining an air chamber in the first cylinder, the air chamber being configurable to accommodate air;
• a drive assembly comprising an electric motor and a linear movement converting unit, the electric motor being electrically connected to the power source and controlled by the control module, the linear movement converting unit being driven by the electric motor and linked to the first piston;
• a guide which is disposed under the cylinder assembly and provided with a channel for receiving a fastener;
• a striker, an upper end of which is linked to the second piston, a lower end of which acts to drive the fastener in the channel into a workpiece, the striker and the second piston having an upper initial position and a lower end position;
• a feed assembly configured to feed the fastener into the channel of the guide;
• and a holding assembly, which holds the second piston and the striker to the initial position before the air chamber is compressed to a predetermined ratio, the second piston and the striker released by the holding assembly moving from the initial position to the end position;
• wherein the fastener driving tool operates with an operating cycle;
• the electric motor adopts a three-phase brushless motor, the electric motor being electrically connected to the power source and being electrically connected, via a control circuit, to the control module;
• and after the fastener driving tool is initiated, the control circuit obtains a rotational speed of the electric motor using a sensorless algorithm and feeds the rotational speed back to the control module, the control module determines an instant stage of the operating cycle as per speed change of the electric motor, and the control module commands the electric motor to stop upon end of the operating cycle.